Anti-torque control using fixed blade pitch motors

ABSTRACT

The present invention includes an a plurality of first variable speed motors mounted on a tail boom of the helicopter; one or more fixed pitch blades attached to each of the plurality of first variable speed motors; and wherein a speed of one or more of the plurality of first variable speed motors is varied to provide an anti-torque thrust.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and is a continuation patentapplication of U.S. patent application Ser. No. 16/886,000, filed on May28, 2020, which is a divisional patent application of U.S. patentapplication Ser. No. 15/458,525, filed on Mar. 14, 2017, now U.S. Pat.No. 10,703,471, which is a continuation-in-part patent application ofU.S. patent application Ser. No. 15/172,811, filed on Jun. 3, 2016, nowU.S. Pat. No. 10,377,479, which are hereby incorporated by reference intheir entirety.

TECHNICAL FIELD OF THE INVENTION

This invention is generally in the field of flight control, and relatesspecifically to an anti-torque system and control for helicopters.

STATEMENT OF FEDERALLY FUNDED RESEARCH

Not applicable.

BACKGROUND OF THE INVENTION

Without limiting the scope of the invention, its background is describedin connection with anti-torque systems.

Counter-torque tail rotors are often used in helicopters and aregenerally mounted adjacent to vertical fins that provide for aircraftstability. In such a configuration, the helicopter rotor produces atransverse airflow. Tail rotors can be driven at high angular velocitiesto provide adequate aerodynamic responses. Sometimes, vortices producedby a main helicopter rotor and the tail rotor can interact to reduce theefficiency of the thrust created by the rotors. The interference of thevortices may also cause an increase in noise. To address these issues,the vertical fin can be replaced by an annular airfoil (sometimes calleda ring wing) having an inner diameter greater than the diameter of thetail rotor and which can be mounted around the tail rotor.

SUMMARY OF THE INVENTION

In one embodiment, the present invention includes an anti-torque modulefor a helicopter comprising: a plurality of first variable speed motorsarranged in a first matrix pattern and mounted on a tail boom of thehelicopter; one or more fixed pitch blades attached to each of theplurality of first variable speed motors; and wherein a speed of one ormore of the plurality of first variable speed motors is varied toprovide an anti-torque thrust. In one aspect, one or more of theplurality of first variable speed motors can operate to provide adirectional thrust: starboard, port, or both starboard and portconcurrently. In another aspect, one or more of the plurality of firstvariable speed motors are at least one of electric or hydraulic motors.In another aspect, the electric motor is at least one of: aself-commutated motor, an externally commutated motor, a brushed motor,a brushless motor, a linear motor, an AC/DC synchronized motor, anelectronic commutated motor, a mechanical commutator motor (AC or DC),an asynchronous motor (AC or DC), a pancake motor, a three-phase motor,an induction motor, an electrically excited DC motor, a permanent magnetDC motor, a switched reluctance motor, an interior permanent magnetsynchronous motor, a permanent magnet synchronous motor, a surfacepermanent magnet synchronous motor, a squirrel-cage induction motor, aswitched reluctance motor, a synchronous reluctance motor, avariable-frequency drive motor, a wound-rotor induction motor, anironless or coreless rotor motor, or a wound-rotor synchronous motor. Inanother aspect, the hydraulic motor is at least one of: a gear and vanemotor, a gerotor motor, an axial plunger motor, a constant pressuremotor, a variable pressure motor, a variable flow motor, or a radialpiston motor. In another aspect, the plurality of first variable speedmotors comprises 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or moremotors that can be at least one of: turned on or off independently,turned on or off as a group, turned one or off in pairs, or each motorcan operate independently to direct thrust in a same or a differentdirection. In another aspect, the module further comprises a ring orcowling surrounding one or more of the plurality of first variable speedmotors and the respective fixed pitch blades, wherein the ring orcowling is attached to a separate pivot, or the ring or cowlingsurrounds all of the plurality of first variable speed motors and therespective fixed pitch blades. In another aspect, the first matrixpattern is planar with the tail boom. In another aspect, the firstmatrix pattern rotates about a longitudinal axis of the tail boom. Inanother aspect, the anti-torque module is round, oval, crescent-shaped,J-shaped, diagonal, square, rectangular, triangular, pentagonal,hexagonal, polygonal, rhomboid, trapezoid, X-shaped, Y-shaped, or kiteshaped. In another aspect, the module further comprises a plurality ofsecond variable speed motors in a second matrix pattern, with respectivefixed pitch blades, that is substantially parallel and planar with thefirst matrix pattern. In another aspect, the plurality of variable speedmotors in the first and second matrix patterns are coaxially alignedwith one another and the fixed pitch blades are outwardly facing. Inanother aspect, two or more of the plurality of first variable speedmotors and fixed pitch blades are selected or operated to have adifferent noise frequency, and the frequencies or speeds are selected tocancel or reduce a noise of the tail rotor during operation. In anotheraspect, the two or more of the plurality of first variable speed motorsare a different size. In another aspect, the two or more of theplurality of fixed pitch blades are a different size. In another aspect,the plurality of fixed pitch blades and first variable speed motors areindividually ducted. In another aspect, each of the plurality of fixedpitch blades and first variable speed motors are on a pivot that allowsfor rotation of the individual fixed pitch blades and first variablespeed motors. In another aspect, the module further comprises a controllogic in a flight control computer for at least one of: calculates theoverall torque generated by the plurality of motors; reduces oreliminates torque; maximize thrust; reduces or eliminates transients;reduces overall tail rotor noise; manages the wear on individual motors;monitors a vortex ring state at the tail rotor; pulses the motors toreduce or eliminate vortex ring states; controls at least one of aposition or the speed of one or motors mounted on individual pivots; orcontrols at least one of a position or the speed of one or motors if theanti-torque module rotates around a longitudinal axis of the tail boom.In another aspect, the module further comprises a rotational sensingsystem that measures a rotation of the helicopter, and a control logicthat comprises a rotation modeling unit that receives rotational datareflective of a rotation of the helicopter to determine changes to thespeed of the first variable speed motors to control or modify therotation of the helicopter. In another aspect, the control logic furthercomprises a filtering unit interposed between the rotational sensingsystem and the first variable speed motors, wherein the filtering unitis configured to remove noise from the data prior to the data beingreceived by the logic, and the logic changes the speed of the one ormore first variable speed motors after removing the noise. In anotheraspect, the control logic further comprises a correction logicconfigured to iteratively correct inaccuracy between an estimated and anactual rotation of the helicopter at a known speed of the one or morefirst variable speed motors. In another aspect, the control logicfurther comprises a correction logic configured to correct inaccuracy inthe rotation of the helicopter by reference to speed data for the one ormore first fixed blade pitch variable speed motors versus rotation ofthe helicopter.

In one embodiment, the present invention includes an anti-torque systemfor a helicopter comprising: a plurality of first variable speed motorsarranged in a first matrix pattern mounted on a tail boom of thehelicopter; one or more fixed pitch blades attached to each of theplurality of first variable speed motors, wherein a speed and directionof the plurality of first variable speed motors and their respectivefixed pitch blades is varied to provide directional thrust; and a logicin a flight control computer for controlling at least one of: the speed,the direction, or both the speed and direction, of the one or more ofthe plurality of first variable speed motors to reduce or eliminatetorque from a main rotor. In one aspect, one or more of the plurality offirst variable speed motors can operate to provide a directional thrust:starboard, port, or both starboard and port concurrently. In anotheraspect, one or more of the plurality of first variable speed motors areat least one of electric or hydraulic motors. In another aspect, thelogic controls at least one of: calculates the overall torque generatedby the plurality of motors; reduces or eliminates torque; maximizethrust; reduces or eliminates transients; reduces overall tail rotornoise; manages the wear on individual motors; monitors a vortex ringstate at the tail rotor; pulses the motors to reduce or eliminate vortexring states; controls at least one of a position or the speed of one ormotors mounted on individual pivots; or controls at least one of aposition or the speed of one or motors if the anti-torque matrix rotatesaround a longitudinal axis of the tail boom. In another aspect, thefirst matrix pattern is substantially planar with the tail boom. Inanother aspect, the plurality of first variable speed motors comprises3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or more motors that can beat least one of: turned on or off independently, turned on or off as agroup, turned one or off in pairs, or each motor can operateindependently to direct thrust in a same or a different direction. Inanother aspect, the system further comprises a ring or cowlingsurrounding one or more of the plurality of first variable speed motorsand the respective fixed pitch blades, wherein the ring or cowling isattached to a separate pivot, or the ring or cowling surrounds all ofthe plurality of first variable speed motors and the respective fixedpitch blades. In another aspect, the anti-torque module is round, oval,crescent-shaped, J-shaped, diagonal, square, rectangular, triangular,pentagonal, hexagonal, polygonal, rhomboid, trapezoid, X-shaped,Y-shaped, or kite shaped. In another aspect, the system furthercomprises a plurality of second variable speed motors in a second matrixpattern, with respective fixed pitch blades, that is substantiallyparallel and planar with the first matrix pattern. In another aspect,the plurality of variable speed motors in the first and second matrixpatterns are coaxially aligned with one another and the fixed pitchblades are outwardly facing. In another aspect, two or more of theplurality of first variable speed motors and fixed pitch blades areselected or operated to have a different noise frequency, and thefrequencies or speeds are selected to cancel or reduce a noise of thetail rotor during operation. In another aspect, two or more of theplurality of first variable motors are a different size. In anotheraspect, two or more of the plurality of fixed pitch blades are adifferent size. In another aspect, one or more of the plurality of fixedpitch blades and first variable motors are individually ducted. Inanother aspect, each of the plurality of fixed pitch blades and firstvariable motors are on a pivot that allows for rotation of theindividual fixed pitch blades and first variable motors.

In another embodiment, the present invention also includes a method ofoperating a helicopter, the method comprising: providing an anti-torquematrix comprising a plurality of first fixed blade pitch variable-speedmotors on a tail boom of the helicopter; and operating one or more ofthe first fixed blade pitch variable-speed motors at one or more speedsto provide at least one of anti-torque thrust or torque thrust, duringhelicopter operations. In one aspect, the method further comprisescalculating or measuring a noise level from each of the plurality offirst fixed blade pitch variable-speed motors or from the anti-torquematrix, and adjusting the speed of each of the one or more first fixedblade pitch variable-speed motors to reduce or eliminate noise duringoperations. In another aspect, the first fixed blade pitchvariable-speed motors are at least one of electric or hydraulic. Inanother aspect, the method further comprises varying a speed of each ofthe individual first fixed blade pitch variable-speed motor in theplurality of first fixed blade pitch variable-speed motors of theanti-torque matrix in a flight mode to adjust at least one of: a torque,a roll, or a yaw of the helicopter. In another aspect, the methodfurther comprises varying a speed of the one or more first fixed bladepitch variable-speed motors by varying the output from each of theindividual fixed blade pitch variable-speed motors for optimum thrustduring helicopter operations. In another aspect, the method furthercomprises pulsing the speed of the one or more first fixed blade pitchvariable-speed motors to reduce or eliminate at least one of: a vortexring state or transients. In another aspect, the method furthercomprises positioning a plurality of second variable speed motors in asecond matrix pattern, with respective fixed pitch blades, that issubstantially parallel and planar with the first matrix pattern. Inanother aspect, the plurality of variable speed motors in the first andsecond matrix patterns are coaxially aligned with one another and thefixed pitch blades are outwardly facing. In another aspect, the methodfurther comprises operating pairs of the plurality of first fixed bladepitch variable-speed motors, wherein one fixed blade pitchvariable-speed motor operates to provide anti-torque thrust and a secondfixed blade pitch variable-speed motor increases or decreases speed ordirection to provide fine control of the overall directional thrust ofthe pair of fixed blade pitch variable-speed motors. In another aspect,the method further comprises at least one of: calculating an overalltorque generated by the plurality of motors; reducing or eliminatingtorque; maximizing a directional thrust; reducing or eliminating one ormore transients; reducing overall tail rotor noise; managing the wear onindividual first fixed blade pitch variable-speed motors; monitoring avortex ring state at the tail rotor; pulsing one or more of the firstfixed blade pitch variable-speed motors to reduce or eliminate vortexring states; controlling at least one of a position or the speed of oneor more first fixed blade pitch variable-speed motors mounted onindividual pivots; or controlling at least one of a position or thespeed of one or more fixed blade pitch variable-speed motors if theanti-torque matrix rotates around a longitudinal axis of the tail boom.In another aspect, the method further comprises calculating, for anequivalent motor speed, the amount of thrust generated by a fixed bladepitch variable-speed motor that is aft from another fixed blade pitchvariable-speed motor, wherein the aft fixed blade pitch variable-speedmotor or motors have a higher torque than a fore fixed blade pitchvariable-speed motor in the first matrix. In another aspect, theanti-torque module is round, oval, crescent-shaped, J-shaped, diagonal,square, rectangular, triangular, pentagonal, hexagonal, polygonal,rhomboid, trapezoid, X-shaped, Y-shaped, or kite shaped.

In yet another embodiment, the present invention includes a helicopterrotation estimation method for use with a helicopter including aplurality of first fixed blade pitch variable speed motors arranged in afirst matrix pattern mounted on a tail boom of the helicopter, themethod comprising: measuring the rotation of the helicopter in responseto a baseline speed of the plurality of first variable speed motorsarranged in a first matrix pattern mounted on a tail boom of thehelicopter; measuring a rotational response of the helicopter to a speedsignal from the one or more of the first variable speed motors; andcomparing the measured rotation of the helicopter to an estimatedrotation of the helicopter to modify the speed of the one or more firstvariable speed motors to achieve a certain rotation of the helicopterbased on a comparison of the estimated and the actual rotation of thehelicopter. In one aspect, the method further comprises obtaining theairspeed of the aircraft from an airspeed sensing system disposed at aforward portion of an airframe of the aircraft and reducing orincreasing the speed of one or more of the plurality of first fixedblade pitch variable speed motors to control a yaw or a response totransients on the helicopter during flight. In one aspect, the step ofcomparing further comprises filtering noise from data reflective of therotation of the helicopter. In another aspect, the step of comparingfurther comprises iteratively correcting data reflective of the rotationof the helicopter between the estimated rotation and the actualrotation. In another aspect, the step of comparing further comprisescorrecting data reflective of the rotation of the helicopter byreference to speed data for the one or more first fixed blade pitchvariable speed motors versus rotation of the helicopter. In anotheraspect, a logic that operates the method is found in a flight controlcomputer.

Yet another embodiment of the present invention is a helicoptercomprising an anti-torque module for a helicopter comprising: aplurality of first variable speed motors arranged in a first matrixpattern and mounted on a tail boom of the helicopter; one or more fixedpitch blades attached to each of the plurality of first variable speedmotors; and wherein a speed of one or more of the plurality of firstvariable speed motors is varied to provide an anti-torque thrust.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the features and advantages of thepresent invention, reference is now made to the detailed description ofthe invention along with the accompanying figures and in which:

FIG. 1 is a side-view schematic diagram of a helicopter showing ananti-torque matrix shown with fixed blade pitch motors.

FIG. 2 shows the use of multiple ducted rotors to generate anti torquethrust.

FIGS. 3A-3F show various schematic diagrams of anti-torque matrix, ofthe present invention that provide higher efficiency and reduced overallsize.

FIGS. 4A-4F show various schematic diagrams of anti-torque matrix, ofthe present invention that provide higher efficiency and reduced overallsize.

FIGS. 5A and 5B show to variants of co-axially positioned motors withoutwardly facing fixed pitch blades of the present invention.

FIGS. 6A and 6B show to variants of co-axially positioned motors withoutwardly facing fixed pitch blades of the present invention.

FIG. 7 shows a flowchart of a control logic for controlling the rotationof a helicopter that comprises the variable speed motors and fixed angleblades in a matrix pattern.

FIG. 8 shows a rotation control system for use with the plurality ofvariable speed motors arranged in a first or a first and a secondmatrix.

DETAILED DESCRIPTION OF THE INVENTION

While the making and using of various embodiments of the presentinvention are discussed in detail below, it should be appreciated thatthe present invention provides many applicable inventive concepts thatcan be embodied in a wide variety of specific contexts. The specificembodiments discussed herein are merely illustrative of specific ways tomake and use the invention and do not delimit the scope of theinvention.

To facilitate the understanding of this invention, a number of terms aredefined below. Terms defined herein have meanings as commonly understoodby a person of ordinary skill in the areas relevant to the presentinvention. Terms such as “a”, “an” and “the” are not intended to referto only a singular entity, but include the general class of which aspecific example may be used for illustration. The terminology herein isused to describe specific embodiments of the invention, but their usagedoes not delimit the invention, except as outlined in the claims.

Most helicopters with a single, main rotor system require a separaterotor to overcome torque. This is traditionally accomplished onhelicopters using a variable pitch, anti-torque rotor or tail rotorreceiving power from the engine(s) through shafts and gearboxes. Whilemany attempts have been made to power a traditional single tail rotordirectly using a large electric motor to replace traditional shafts andgearboxes. These attempts proved to be impractical however clue to theexcessive weight of an electric motor capable of providing the requiredtorque and speed to power a traditional tail rotor. Additionally thesafety reliability of a single or even a dual electric motor does notapproach the safety reliability of shafts and gearboxes.

The present invention is directed to an anti-torque control using amatrix of fixed blade pitch motor modules resolves the excessive weightand safety reliability issues with electrically powered anti-torque byutilizing a matrix of small fixed blade pitch electric motor modules inplace of a traditional tail rotor.

The present invention has certain advantages over prior tail-rotorconfigurations. One such advantage is the low rotational inertia of theindividual fixed blade pitch motors (e.g., electrically, hydraulically,or pneumatically driven motors) that together form the anti-torquematrix, wherein the individual motors can be individually controlled tohave their speed and direction changed rapidly. The present inventionalso eliminates the complexity of a variable blade pitch system. Anadvantage of the present invention includes the use of small size offixed blade pitch electric motor modules provides adequate convectioncooling, eliminating requirement for active cooling system. Further,operating a large number of fixed blade pitch electric motor modulesprovides safety reliability from component failures through a high levelof redundancy without excessive weight. In addition, the widedistribution of fixed blade pitch electric motor modules provides forincreased safety from external threats such as collision and lightening.Also, when a helicopter is on the ground with main rotor turning, thelower inertia of the fixed blade pitch electric motor modules and theability to shut them down completely reduces the injury risk from bladecontact to personnel. Moreover, the present invention increases cruiseefficiency by slowing down or stopping selected fixed blade pitchelectric motor modules. Another important advantage of the presentinvention is reduced passenger noise and vibration by operating thematrix of fixed blade pitch electric motor modules at slower speeds, orstopping selected fixed blade pitch electric motor modules. The presentinvention also reduces objectionable ground noise in hover by operatingthe matrix of fixed blade pitch electric motor modules at differentindividual speeds to distribute frequencies across a wide band. Duringoperation, the present invention can increase stability during flight byproviding a yaw stability augmentation capability through fly-by-wirecontrols. Finally, the speed of fixed blade pitch electric motor modulescan be increased when operating at higher altitudes to compensate fordecrease in thrust. The present invention also provides an increase incruise efficiency through directional optimization of thrust angle ofthe anti-torque matrix.

The present invention includes a convertible helicopter anti-torquematrix that uses fixed blade pitch electrically or hydraulically-drivenmotors, variable-speed motors for ground and low speed forward flight.The entire anti-torque matrix, or individual motors, pairs of motors, orother combinations of motors, can have a surrounding ring or cowlingthat acts in place of a traditional tail rotor of a helicopter and thatis connected to the helicopter via a pivot that can be used to directthe thrust of one or more motors of the anti-torque matrix.Alternatively, individual fixed blade pitch electrically orhydraulically-driven, variable-speed motors can each have a surroundingring or cowling that is connected to a pivot. The combined blades of thevarious tail rotor motors that form the module can each provide separatethrust. The anti-torque matrix fixed can include two, three, four, five,six, seven, eight, nine, ten or more individual fixed blade pitchvariable-speed motors, which can operate alone or in one or morecombinations and in one or more directions. Further, the presentinvention includes having co-axial (or offset) pairs of motors that arepositioned in parallel to provide outward thrust.

When provided within a cowling, the various vortices can be captured toform a circulating air pattern, which can act as a pump to drawadditional air through the center of the fixed blade pitch electricallyor hydraulically-driven, variable-speed motors from the region adjacentthe upstream surface of motors. The circulating air pattern and eductioncan increase the diameter of the wake and the volume of air transportedby the anti-torque matrix. The wake of the anti-torque matrix can betransported at a slow rate while including a greater mass of air by theoperation of the combined fixed blade pitch electrically orhydraulically-driven, variable-speed motors, thus resulting in increasedefficiency in the operation of the overall anti-torque matrix that actsas a tail rotor.

By using smaller individual electric motors, each having their own fixedpitch propeller, the overall rotational energy of each propeller is muchsmaller and can even use softer or even frangible materials that willprotect any ground crews when coming into contact during a hover or slowflight, while still providing the additive aerodynamic forces to controlaircraft yaw, roll or pitch in forward flight.

The fixed blade pitch electrically or hydraulically-driven,variable-speed motors can provide longitudinal pitch trim and lateralyaw trim. In cruise mode, the flow axis of the fixed blade pitchelectrically or hydraulically-driven, variable-speed motors is alignedgenerally with or along the long axis of the fuselage to serve as ahorizontal stabilizer. In hover mode, the arrangement of the fixed bladepitch electrically or hydraulically-driven, variable-speed motorseliminates the down load of a horizontal tail surface that may arise dueto interference with the down wash from the main rotor. The fixed bladepitch electrically or hydraulically-driven, variable-speed motors canalso off-load the anti-torque matrix in forward flight by positioningitself with a yaw-direction incidence angle via a pilot trim control,thereby reducing power consumption. The anti-torque matrix presents asurface area in sideward flight, and can thereby serve in a passive rollas a yaw damper. The anti-torque matrix can also help reduce the size ofa horizontal stabilizer. Alternatively or in addition, application ofthe anti-torque matrix can allow for the elimination of both verticaland horizontal surfaces normally utilized on conventional helicopters.This can allow a reduction in weight, download for a horizontalstabilizer in the rotor wake and reduced projected side area and drag inlateral (side) flight.

The present invention addresses the limitations of current electricmotor technology and takes advantage or the unique performancecapabilities of electric motors for use in helicopter anti torquecontrol. Currently available electric motor technology has limitedpracticality for use as direct replacements of mechanical drive trains,turbine engines or internal combustion (IC) engines on aircraft. This isbecause in spite of recent advances in electric motor and batterytechnology, the comparable power density (power output per unit weightof a motor) becomes less practical with increasing motor size. This iswhy electric motors work so well on small, unmanned aircraft, but arestill impractical for more than limited range use on very fight fixedwing aircraft.

The invention takes advantage of the unique performance capabilities ofelectric motors for use in helicopter anti-torque control. Using thisdistributed electric propulsion design and today's flight controltechnology, each motor can be controlled independently to varyindividual motor thrust, and thereby position the anti-torque matrix(hinged at the center and free to rotate about the vertical axis) foroptimum overall thrust (direction and magnitude). In hover mode, ahelicopter requires anti-torque thrust perpendicular to the airframe'scenterline. As the helicopter increases its forward airspeed, thisperpendicular thrust requirement reduces. As the anti-torque thrustrequirement reduces, the speed of the motors can be varied to optimizepower utilization and overall aircraft performance.

Since electric motor power density becomes less practical withincreasing motor size, “distributed propulsion” makes use a largerquantity of smaller motors. Combining the shaft output of multiple smallmotors into a single shaft output using a gearbox wipes out any weightsavings and introduces thermal issues, which can require the addition offluid cooling systems and even more weight. However, by distributingmultiple small motors over the airframe, the total aircraft structuralweight can be reduced by spreading smaller propulsion induced loadsacross the entire aircraft. Separating the motors by at least a rotordiameter also provides effective convection cooling. With existingelectric power storage technology (batteries, fuel cells) theapplication of distributed propulsion on manned fixed wing aircraft isbecoming more practical, but range is very limited. In the event ofdepletion of stored energy a fixed wing aircraft can still possiblyglide to a safe landing. This is not the same case with application ofDistributed Propulsion for lift propulsion on helicopters. Onhelicopters with distributed propulsion, the rotational inertia of themultiple small rotors is inadequate to support autorotation for safelanding. This combined with the higher power demands required forvertical lift rotors makes pure electric helicopters impractical until adramatic increase in electric power storage technology occurs.

On manned helicopter configurations incorporating distributedpropulsion, a dedicated system for anti-torque control is not required.Multiple small rotors cancel out each others torque and changing rotorspeeds can generate control yaw. Therefore, the application ofDistributed Propulsion specifically for anti-torque control appears tohave been overlooked.

For example, using a Bell model 407 tail rotor for sizing analysis,using existing commercially available electric Sport Light applicationelectric motors and propellers, it is possible to generate equivalentthrust with a matrix of 3×3 or 4×4 fixed blade pitch electric motormodules in approximately the same disc area. With an approximate fixedblade pitch electric motor module conservative weight of 5 pounds (2.2kilos) (for 3×3 matrix), the total weight minus structure and systeminstallation is 45 pounds (20 kilos). This weight is comparable to thecurrent 407 rotor and gearbox weight. The one starter/generator on the407 does not provide adequate power or reliability to support operationof the matrix of fixed blade pitch motor modules of the presentinvention. However, the elimination of the tail rotor output shaftprovides for a main gearbox accessory drive pad to mount redundantgenerators. Because the added generator capacity is over sized forsafety reliability, with both generators operating approximately 40 kWpower can be made available for non-flight critical uses. Similarcalculations apply to the use of hydraulic motors.

Another advantage of the use of a matrix of fixed blade pitch motormodules is that, in the event of loss of all aircraft engine power, thepower demand for anti-torque control thrust becomes minimal. Therefore,the impact on the aircrafts electric power systems and rotor energy isalso minimal in the event of an auto rotation landing. With increasingforward flight speed the interaction of airflow between rotors resultsin the aft-most rotors losing their effectiveness. Commensurately, withincreasing forward speed the anti-torque thrust required decreases.Therefore with increasing forward speed the aft most modules will beprogressively shut off to eliminate unneeded power consumption andreduce noise.

The present invention can use at least one of an electric and/or ahydraulic motor. Non-limiting examples of electric motors for use withthe present invention include: a self-commutated motor, an externallycommutated motor, a brushed motor, a brushless motor, a linear motor, anAC/DC synchronized motor, an electronic commutated motor, a mechanicalcommutator motor (AC or DC), an asynchronous motor (AC or DC), a pancakemotor, a three-phase motor, an induction motor, an electrically excitedDC motor, a permanent magnet DC motor, a switched reluctance motor, aninterior permanent magnet synchronous motor, a permanent magnetsynchronous motor, a surface permanent magnet synchronous motor, asquirrel-cage induction motor, a switched reluctance motor, asynchronous reluctance motor, a variable-frequency drive motor, awound-rotor induction motor, an ironless or coreless rotor motor, or awound-rotor synchronous motor. Non-limiting examples of hydraulic motorsfor use with the present invention include: a gear and vane motor, agerotor motor, an axial plunger motor, a constant pressure motor, avariable pressure motor, a variable flow motor, or a radial pistonmotor.

FIG. 1 is a side-view schematic diagram of a helicopter 100 having theanti-torque matrix 110, depicted in this version with nine fixed bladepitch motors 112 a-112 i, which can be fixed blade pitch electrically orhydraulically-driven and/or variable-speed motors. The helicopter 100includes a rotary system 102 carried by a fuselage 104. Rotor blades 106connected to the rotary system 102 provide flight for the helicopter100. The rotor blades 106 are controlled by multiple controllers withinthe fuselage 104. For example, during flight, a pilot can manipulatecyclic controllers (not shown) for changing a pitch angle of the rotorblades 106 and/or manipulate pedals (not shown) to provide vertical,horizontal and yaw flight control. The helicopter 100 has a tail boom108, which supports the anti-torque matrix 110 at the aft end. Each ofthe fixed blade pitch motors 112 a-112 i can be operated individually orin groups to provide counter-torque force for transversely stabilizingthe helicopter 100. Each of the fixed blade pitch motors 112 a-112 i ismounted as part of the anti-torque matrix 110 on the tail boom 108. Theanti-torque matrix 110 is centered on a hub such that a leading edge ofthe anti-torque matrix 110 is presented to the side of the helicopter100 toward the tail boom 108. For example, when a single main rotor thehelicopter 100 is rotating counter-clockwise when viewed from above, theleading edge of anti-torque matrix 110 is to the right (starboard) sideof the helicopter 100.

FIG. 2 shows the use of multiple ducted rotors to generate anti torquethrust. In this example a helicopter 100 has the anti-torque matrix 110,depicted in this version with nine fixed blade pitch motors 112 a-112 i,which can be fixed blade pitch electrically or hydraulically-drivenand/or variable-speed motors, each of which are individually ducted. Theanti-torque matrix 110 can further include a surface 114 that forms partof the ducting for the nine fixed blade pitch motors 112 a-112 i. As isthe case with the helicopter in FIG. 1, the helicopter 100 includes arotary system 102 carried by a fuselage 104. Rotor blades 106 connectedto the rotary system 102 provide flight for the helicopter 100. Therotor blades 106 are controlled by multiple controllers within thefuselage 104. For example, during flight, a pilot can manipulate cycliccontrollers (not shown) for changing a pitch angle of the rotor blades106 and/or manipulate pedals (not shown) to provide vertical, horizontaland yaw flight control. The helicopter 100 has a tail boom 108, whichsupports the anti-torque matrix 110 at the aft end, which also permitsrotation of the anti-torque matrix 110 about the longitudinal axis ofthe tail boom 108. Each of the fixed blade pitch motors 112 a-112 i canbe operated individually or in groups to provide counter-torque forcefor transversely stabilizing the helicopter 100. Each of the fixed bladepitch motors 112 a-112 i is mounted as part of the anti-torque matrix110 on the tail boom 108. The anti-torque matrix 110 is centered on ahub such that a leading edge of the anti-torque matrix 110 is presentedto the side of the helicopter 100 toward the tail boom 108. For example,when a single main rotor the helicopter 100 is rotatingcounter-clockwise when viewed from above, the leading edge ofanti-torque matrix 110 is to the right (starboard) side of thehelicopter 100.

In operation, the anti-torque matrix 110 is oriented substantiallyin-plane with the tail boom 108 of the helicopter 100 during a firstmode of helicopter operation. The skilled artisan will recognize thatthe anti-torque matrix 110 may be a first anti-torque matrix 110, with asecond anti-torque matrix 110 that is substantially parallel to thefirst providing additional motors and fixed pitch blades that,generally, will be facing outwardly from each other, with the motorsbeing in the center of the anti-torque matrix 110. Generally, the motorswill be co-axial, however, in certain embodiments the motors do not haveto be co-axial. Further, while FIGS. 1 and 2 shows the anti-torquematrix 110 are being in the form of a 3×3 matrix, that is generallyrhomboid in shape, the skilled artisan will recognize that theanti-torque matrix 110 can have any shape and include 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14, 15 or more motors, which motors could also bein co-axial pairs. Further, the anti-torque matrix 110 can have anyshape, such as round, oval, crescent-shaped, J-shaped, diagonal, square,rectangular, triangular, pentagonal, hexagonal, polygonal, rhomboid,trapezoid, X-shaped, Y-shaped, or kite shaped,

For example, the first mode of helicopter operation is a hover mode,which is typically a mode in which the helicopter 100 is sitting on orabout the ground with the anti-torque matrix 110 provides thrust fromthe one or more fixed blade pitch motors 112 a-112 i when the helicopter100 is operating in slow speed flight. In this orientation, theanti-torque matrix 110 can provide maneuverability and trim to thehelicopter operation. During hover, the direction of thrust of the oneor more fixed blade pitch motors 112 a-112 i of the anti-torque matrix110 can be in opposing directions, for example, one subset of motors candirect their thrust in one direction, while another subset can bedirected in the opposite direction to provide finer rotational controlto the helicopter 100. Of course, the speed of the individual motors canalso be varied, under control of a logic in a flight control computerthat calculates the position of the anti-torque matrix 110 duringtransition to and from the first to the second mode of operation and forindependently controlling individual fan speeds to position the matrixfor optimum thrust angle, as well as optimum thrust magnitude.

In a second mode of operation, the anti-torque matrix 110 is orientedsubstantially off-plane with the tail boom 108 of the helicopter 100during a second mode of helicopter operations that is different from thefirst mode. For example, the second mode of helicopter operation is aflight mode (e.g., a low to high speed forward flight mode). In theflight mode, the orientation of the anti-torque matrix 110 is changedfrom being substantially co-planar with the tail boom 108 to beingnon-planar. For example, the anti-torque matrix 110 can be substantiallyperpendicular with the plane of the tail boom 108, by pivoting aboutpivot. Alternatively, the orientation of the anti-torque matrix 110 canbe anywhere between co-planar and perpendicular relative to the tailboom 108.

FIGS. 3A-3F and FIGS. 4A-4F show several variations of the matrixpatterns of the variable speed motors of the present invention thatprovide higher efficiency and reduced overall size. The skilled artisanwill recognize that there are an infinite number of possible variationsof number of rotors and pattern of rotor positions when using 2, 3, 4,5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or more electric and/or hydraulicmotors. Of course, the different motors could also be ducted in groupsof 2, 3, 4, 5, or more, again, having a variety of shapes and sizes. Inaddition, different motors could be different sizes and also the bladescould also vary in size throughout the matrix.

FIGS. 3A to 3F, and 4A to 4F show various schematic diagrams ofanti-torque matrix with the tail boom 108 of the helicopter 100. In FIG.3A the anti-torque matrix 300 is mounted to the tail boom 108 having asurface 114 and is depicted as having various electric motors and fixedpitch angle blades that are of different sizes and generally forming atriangular shape, with the apex of the triangle facing aft and theanti-torque matrix 110 being generally vertical. FIG. 4A shows the sameconfiguration as in FIG. 3A, in this case the anti-torque matrix 400 isdepicted with a pivot 412. FIG. 3B shows an anti-torque matrix 302 ismounted to, or integral with, the tail boom 108 having a surface 114 andis depicted as having a J-shape in which the various electric motors andfixed pitch angle blades have about the same size and are ducted. FIG.4B shows a same configuration as in FIG. 3B, in this case theanti-torque matrix 402 is depicted with a pivot 412. However, in thisconfiguration the anti-torque matrix 402 shows a combination of in-planevariable speed motors and off-plane variable speed motors, which canalso apply to all the configurations shown herein. FIG. 3C shows ananti-torque matrix 304 is mounted to the tail boom 108 having surfaces114 a and 114 b and is depicted as having various electric motors andfixed pitch angle blades that are about the same size and generally forma triangular shape with the apex of the triangle facing forward. In FIG.3C, the anti-torque matrix 304 oriented off-plane with the tail boom 108of the helicopter 100, that is, the anti-torque matrix 304 has beenrotated on a Z-axis that passes between the upper end axis 114 a and thelower end axis 114 b perpendicular from an in-plane orientation. In someimplementations, the anti-torque matrix 304 can be pivoted on ahorizontal X-axis to provide yaw control of the helicopter 100. FIG. 4Cshows the same configuration as in FIG. 3C, in this case the anti-torquematrix 404 is depicted with a pivot 412. FIG. 3D shows an anti-torquematrix 306 is mounted to the tail boom 108 having surfaces 114 a and 114b and is depicted as having various electric motors and fixed pitchangle blades that are about the same size and generally form atriangular shape with the apex of the triangle facing forward, however,in this embodiment the fork is horizontal. FIG. 4D shows the sameconfiguration as in FIG. 3D, in this case the anti-torque matrix 406 isdepicted with a pivot 412. FIG. 3E shows an anti-torque matrix 308 ismounted to the tail boom 108 having a surface 114 and is depicted ashaving various electric motors and fixed pitch angle blades that areabout the same size and generally form an X-shape, with two additionalmotors. FIG. 4E shows the same configuration as in FIG. 3E, in this casethe anti-torque matrix 408 is depicted with a pivot 412. FIG. 3F showsan anti-torque matrix 310 is mounted to the tail boom 108 havingsurfaces 114 a and 114 b and is depicted as having various electricmotors and fixed pitch angle blades that are about the same size andgenerally form a crescent shape with the apex of the crescent facingforward. FIG. 4F shows the same configuration as in FIG. 3F, in thiscase the anti-torque matrix 410 is depicted with a pivot 412.

FIGS. 4A to 4F shows that a pivoting mechanism can be included with oneor more of the fixed pitch rotors in the anti-torque matrix 400-410 atthe end of the tail boom 108 of the helicopter 100. In someimplementations, the pivoting mechanism can be electric, or can even bea bell crank system and can include a pulley cable system connected tothe bell crank system. The pivoting mechanism can be controlled by anoperator of the helicopter 100 to orient the anti-torque matrix 400-410substantially in-plane with the tail boom 108 of the helicopter 100during a first mode of helicopter operation, and to orient theanti-torque matrix 400-410 substantially off-plane with the tail boom108 of the helicopter 100 during a second mode of helicopter operationthat is different from the first mode. In a fly-by-wire configuration,the pivoting mechanism can be controlled by a logic in a flight controlcomputer that calculates the position of the anti-torque matrix 400-410during transition to and from the first to the second mode of operationand for independently controlling individual fan speeds to position thematrix for optimum thrust angle, as well as optimum thrust magnitude.

FIG. 5A is an rear, end view of the anti-torque matrix 110 depicted inthis version as sitting on the tail boom 108, wherein the anti-torquematrix 110 can be included at the end of the tail boom 108 comprises twoparallel sets of variable speed motors and fixed angle blades 502 a to502 f, that are shown within the body of the anti-torque matrix 110,wherein the variable speed motors 502 a to 502 f are co-axial and theblades are outwardly facing. Each pair of coaxial motors (502 a and 502f, 502 b and 502 e, and 502 c and 502 d) is depicted as being within aduct 504 a, 504 b, 504 c, respectively, and shows three pairs of motorsthat are internal to the tail boom. The skilled artisan will recognizethat if the anti-torque matrix 110 has 6, 9, 12, or other number ofpairs of motors, the end view only permits showing, in this version, theclosest motors (502 a-502 f), however, additional pairs of motors andducts can also be found forward from these motors.

FIG. 5B is an rear, end view of the anti-torque matrix 110 depicted inthis version as sitting on the tail boom 108, wherein the anti-torquematrix 110 can be included at the end of the tail boom 108 comprises twoparallel sets of variable speed motors and fixed angle blades 502 a to502 f, that are shown to extend from the mast 506 of the anti-torquematrix 110, wherein the variable speed motors 502 a to 502 f areco-axial and the blades are outwardly facing. Each pair of coaxialmotors (502 a and 502 f, 502 b and 502 e, and 502 c and 502 d) isdepicted as being within a duct 504 a, 504 b, 504 c, respectively, andshows three pairs of motors. The skilled artisan will recognize that ifthe anti-torque matrix 110 has 6, 9, 12, or other number of pairs ofmotors, the end view only permits showing, in this version, the closestmotors (502 a-502 f), however, additional pairs of motors and ducts canalso be found forward from these motors.

FIGS. 6A and 6B show the same configuration as FIGS. 5A and 5B, but inthis configuration the motors 602 a-602 f are connected to a pivotingmechanism 612. The pivoting mechanism 612 can be electric, mechanical,or can even be a bell crank system and can include a pulley cable systemconnected to the bell crank system. In the configurations shown in FIGS.6A and 6B, the aft portion of the anti-torque matrix 110 is fitted withrearward grooves or openings in the aft portion of the tail rotor, forexample, at mast 606, to add thrust to the rotorcraft. The pivotingmechanism can be controlled by an operator of the helicopter 100 toorient the anti-torque matrix 110 substantially in-plane with the tailboom 108 of the helicopter 100 during a first mode of helicopteroperation, and to orient the anti-torque matrix 110 substantiallyoff-plane with the tail boom 108 of the helicopter 100 during a secondmode of helicopter operation that is different from the first mode. In afly-by-wire configuration, the pivoting mechanism can be controlled by alogic in a flight control computer that calculates the position of theanti-torque matrix 110 during transition to and from the first to thesecond mode of operation and for independently controlling individualfan speeds to position the matrix for optimum thrust angle, as well asoptimum thrust magnitude.

FIG. 7 shows a flowchart of a control logic 700 for controlling therotation of a helicopter that comprises the variable speed motors andfixed angle blades in a matrix pattern. In step 702, the control logic700 that can be, e.g., in a flight control computer, receivesmeasurements of the rotation of the helicopter from, e.g., a rotationsensor. In step 704, the control logic 700 changes the speed of the oneor more variable speed motors to increase torque or anti-torque to adesired rotation, which rotation can include no rotation. The controllogic 700 can include looking up a table of known or estimated torquecalculations or formulas for each of the variable speed motors dependingon the size of the motor, fixed pitch blade, or position in the matrix.The position of the variable speed motors in the matrix willsignificantly affect their individual effect on the rotation of thehelicopter. For example, assuming all the variable speed motors andfixed pitch blades are of equivalent size and power, then the variablespeed motors and fixed pitch blades that are at the aft-most positionwill have the greatest effect on torque, while variable speed motors andfixed pitch blades that are fore from other motors will have lessoverall torque, assuming the same speed. As such, the control logic 700can look-up the estimated or measured effect on torque for eachindividual motor (or pairs of motors if co-axial), and then increase ordecrease the speed to adjust the rotation of the helicopter. In step706, the control logic 700 receives data from the rotation sensor thatreflects actual helicopter rotation and in step 708, compares theestimate or calculated rotation of the helicopter versus actual rotationand can then adjust motor speed to change the speed of one or more ofthe variable speed motors and fixed pitch blades to control rotation, ifany.

FIG. 8 shows a rotation control system 800 for use with the plurality ofvariable speed motors arranged in a first or a first and a secondmatrix. A control logic 802 is connected to a rotation sensor 804. Thecontrol logic 802 is also connected and controls the speed of the one ormore fixed pitch blade variable speed motors 810 a-810 i that are partof anti-torque module 808. The control logic 802 is also connected to atable 806 that includes the calculated torque versus speed for each ofthe one or more fixed pitch blade variable speed motors 810 a-810 i. Thecontrol logic 802 looks up estimated torques for the motors to adjustthe speed of the motors based on a user-input for overall helicopterrotation (if any), then measures actual rotation, and finally adjuststhe speed and torque of the one or more fixed pitch blade variable speedmotors 810 a-810 i during flight operations.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made without departingfrom the spirit and scope of the disclosure. In some implementations,the fixed blade pitch electric motor module can be controlled by pilotinputs in combination with the operating status of the air vehicle(e.g., hover, transition or forward flight). In implementations in whichthe rotorcraft is operated using some form of fly-by-wire orfly-by-light control systems, the fixed blade pitch electric motormodule operation can be controlled by the computer system, which, inturn, can get cues from the pilot's inputs, etc.

All publications and patent applications mentioned in the specificationare indicative of the level of skill of those skilled in the art towhich this invention pertains. All publications and patent applicationsare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

The use of the word “a” or “an” when used in conjunction with the term“comprising” in the claims and/or the specification may mean “one,” butit is also consistent with the meaning of “one or more,” “at least one,”and “one or more than one.” The use of the term “or” in the claims isused to mean “and/or” unless explicitly indicated to refer toalternatives only or the alternatives are mutually exclusive, althoughthe disclosure supports a definition that refers to only alternativesand “and/or.” Throughout this application, the term “about” is used toindicate that a value includes the inherent variation of error for thedevice, the method being employed to determine the value, or thevariation that exists among the study subjects.

As used in this specification and claim(s), the words “comprising” (andany form of comprising, such as “comprise” and “comprises”), “having”(and any form of having, such as “have” and “has”), “including” (and anyform of including, such as “includes” and “include”) or “containing”(and any form of containing, such as “contains” and “contain”) areinclusive or open-ended and do not exclude additional, unrecitedelements or method steps. In embodiments of any of the compositions andmethods provided herein, “comprising” may be replaced with “consistingessentially of” or “consisting of”. As used herein, the phrase“consisting essentially of” requires the specified integer(s) or stepsas well as those that do not materially affect the character or functionof the claimed invention. As used herein, the term “consisting” is usedto indicate the presence of the recited integer (e.g., a feature, anelement, a characteristic, a property, a method/process step or alimitation) or group of integers (e.g., feature(s), element(s),characteristic(s), propertie(s), method/process steps or limitation(s))only.

The term “or combinations thereof” as used herein refers to allpermutations and combinations of the listed items preceding the term.For example, “A, B, C, or combinations thereof” is intended to includeat least one of: A, B, C, AB, AC, BC, or ABC, and if order is importantin a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB.Continuing with this example, expressly included are combinations thatcontain repeats of one or more item or term, such as BB, AAA, AB, BBC,AAABCCCC, CBBAAA, CABABB, and so forth. The skilled artisan willunderstand that typically there is no limit on the number of items orterms in any combination, unless otherwise apparent from the context.

As used herein, words of approximation such as, without limitation,“about”, “substantial” or “substantially” refers to a condition thatwhen so modified is understood to not necessarily be absolute or perfectbut would be considered close enough to those of ordinary skill in theart to warrant designating the condition as being present. The extent towhich the description may vary will depend on how great a change can beinstituted and still have one of ordinary skilled in the art recognizethe modified feature as still having the required characteristics andcapabilities of the unmodified feature. In general, but subject to thepreceding discussion, a numerical value herein that is modified by aword of approximation such as “about” may vary from the stated value byat least ±1, 2, 3, 4, 5, 6, 7, 10, 12 or 15%.

All of the compositions and/or methods disclosed and claimed herein canbe made and executed without undue experimentation in light of thepresent disclosure. While the compositions and methods of this inventionhave been described in terms of preferred embodiments, it will beapparent to those of skill in the art that variations may be applied tothe compositions and/or methods and in the steps or in the sequence ofsteps of the method described herein without departing from the concept,spirit and scope of the invention. All such similar substitutes andmodifications apparent to those skilled in the art are deemed to bewithin the spirit, scope and concept of the invention as defined by theappended claims.

What is claimed is:
 1. An aircraft comprising: a tail boom; a pluralityof first variable-speed motors mounted on the tail boom; and a controllogic configured to: measure a rotation of the aircraft in response to abaseline speed of the plurality of first variable-speed motors; change aspeed of one or more of the plurality of first variable-speed motors;measure a change in the rotation of the aircraft in response to thechange in the speed of the one or more of the plurality of firstvariable-speed motors; determine an estimated change in the rotation ofthe aircraft based on the change in the speed of the one or more of theplurality of first variable-speed motors; compare the measured change inthe rotation of the aircraft to the estimated change in the rotation ofthe aircraft; and modify the speed of one or more of the plurality offirst variable-speed motors based on the comparison.
 2. The aircraft ofclaim 1, wherein the control logic is further configured to obtain anairspeed of the aircraft from an airspeed sensing system disposed at aforward portion of an airframe of the aircraft and reduce or increasingthe speed of one or more of the plurality of first fixed blade pitchvariable-speed motors to control a yaw or a response to transients onthe aircraft during flight.
 3. The aircraft of claim 1, wherein thecontrol logic is further configured to: filter a noise from a datareflective of the change in the rotation of the aircraft; iterativelycorrect the data reflective of the change in rotation of the aircraftbetween the estimated change in rotation and the measured change inrotation; or provide a directional thrust using at least one of theplurality of first variable-speed motors, and the directional thrustcomprises a starboard thrust, a port thrust, or both the starboardthrust and the port thrust concurrently.
 4. The method of claim 1,wherein the control logic compares the measured change to the estimatedchange by correcting data reflective of the change in rotation of theaircraft by reference to speed data for the one or more of the pluralityof first variable-speed motors versus the change in rotation of theaircraft.
 5. The aircraft of claim 1, wherein the estimated change inthe rotation of the aircraft comprises no change in rotation of theaircraft, or an adjustment in a torque, a roll, or a yaw of theaircraft.
 6. The aircraft of claim 1, wherein the control logic isfurther configured to calculate an overall torque generated by theplurality of first variable-speed motors, reduce or eliminate a torque,reduce or eliminate transients, maximize a thrust, reduce an overalltail rotor noise, manage wear on each of the plurality of firstvariable-speed motors, monitor a vortex ring state at a tail rotor,pulse the plurality of first variable-speed motors to reduce oreliminate the vortex ring state, control at least one of a position or aspeed of one or more of the plurality of first variable-speed motorsmounted on individual pivots, or control at least one of the position orthe speed of the plurality of first variable-speed motors if theplurality of first variable-speed motors rotate around a longitudinalaxis of the tail boom.
 7. The aircraft of claim 1, further comprising aplurality of second variable-speed motors mounted on the tail boom ofthe aircraft that are substantially parallel and planar with theplurality of first variable-speed motors.
 8. The aircraft of claim 7,wherein the plurality of first variable-speed motors are coaxiallyaligned with the plurality of second variable-speed motors.
 9. Theaircraft of claim 1, wherein: the plurality of first variable-speedmotors are at least one of electric or hydraulic motors; one or more ofthe plurality of first variable-speed motors are a different size; theplurality of first variable-speed motors are arranged in a round, oval,crescent-shaped, J-shaped, diagonal, square, rectangular, triangular,pentagonal, hexagonal, polygonal, rhomboid, trapezoid, X-shaped,Y-shaped, or kite-shaped pattern; the plurality of first variable-speedmotors can be turned on or off independently, turned on or off as agroup, turned one or off in pairs, or each of the plurality of firstvariable-speed motors can operate independently to direct thrust in asame or a different direction; the plurality of first variable-speedmotors are rotatable about a longitudinal axis of the tail boom; or eachof the plurality of first variable-speed motors is on a pivot thatallows for rotation of the first variable-speed motor.
 10. The aircraftof claim 1, further comprising: one or more fixed pitch blades attachedto each of the plurality of first variable-speed motors; and wherein:the one or more of the one or more fixed pitch blades are a differentsize; a torque of each of the plurality of first variable-speed motorsand the respective fixed pitch blade is based on a size, power andposition of the first variable-speed motor and the respective fixedpitch blade; the plurality of first variable-speed motors and therespective fixed pitch blades are individually ducted; or a ring orcowling surrounds one or more of the plurality of first variable-speedmotors and the respective fixed pitch blades.
 11. An aircraftcomprising: a tail boom; three or more variable-speed motors mounted onthe tail boom; and a control logic configured to: measure a rotation ofthe aircraft in response to a speed of the three or more variable-speedmotors; change a speed of one or more of the three or morevariable-speed motors to achieve an estimated rotation of the aircraft;measure an actual rotation of the aircraft; compare the estimatedrotation of the aircraft to the actual rotation of the aircraft; andadjust the speed of one or more of the three or more variable-speedmotors based on the comparison.
 12. The aircraft of claim 11, whereinthe estimated rotation of the aircraft comprises no change in rotationof the aircraft, or an adjustment in a torque, a roll, or a yaw of theaircraft.
 13. The aircraft of claim 11, wherein the control logic isfurther configured to: look up an estimated or measured effect on atorque for each of the three or more variable-speed motor or pairs ofthe three or more variable-speed motors; and determine the estimatedrotation of the aircraft based on the estimated or measured effect onthe torque.
 14. The aircraft of claim 11, wherein the control logic isfurther configured to calculate an overall torque generated by theplurality of first variable-speed motors, reduce or eliminate a torque,reduce or eliminate transients, maximize a thrust, reduce an overalltail rotor noise, manage wear on each of the plurality of firstvariable-speed motors, monitor a vortex ring state at a tail rotor,pulse the plurality of first variable-speed motors to reduce oreliminate the vortex ring state, control at least one of a position or aspeed of one or more of the plurality of first variable-speed motorsmounted on individual pivots, or control at least one of the position orthe speed of the plurality of first variable-speed motors if theplurality of first variable-speed motors rotate around a longitudinalaxis of the tail boom.
 15. The aircraft of claim 11, wherein the threeor more variable-speed motors comprise: three or more firstvariable-speed motors; and three or more second variable-speed motorsthat are substantially parallel and planar with the three or more firstvariable-speed motors.
 16. The aircraft of claim 15, wherein the threeor more first variable-speed motors are coaxially aligned with the threeor more second variable-speed motors.
 17. The aircraft of claim 15,further comprising one or more fixed pitch blades attached to each ofthe three or more first variable-speed motors and the three or moresecond variable-speed motors, wherein all the fixed pitch blades areoutwardly facing.
 18. The aircraft of claim 11, wherein the controllogic is further configured to provide a directional thrust using atleast one of the three or more variable-speed motors, and thedirectional thrust comprises a starboard thrust, a port thrust, or boththe starboard thrust and the port thrust concurrently.
 19. The aircraftof claim 11, wherein: the three or more variable-speed motors are atleast one of electric or hydraulic motors; one or more of the three ormore variable-speed motors are a different size; the three or morevariable-speed motors are arranged in a round, oval, crescent-shaped,J-shaped, diagonal, square, rectangular, triangular, pentagonal,hexagonal, polygonal, rhomboid, trapezoid, X-shaped, Y-shaped, orkite-shaped pattern; the three or more variable-speed motors can beturned on or off independently, turned on or off as a group, turned oneor off in pairs, or each of the three or more variable-speed motors canoperate independently to direct thrust in a same or a differentdirection; the three or more variable-speed motors are rotatable about alongitudinal axis of the tail boom; or each of the three or morevariable-speed motors is on a pivot that allows for rotation of thefirst variable-speed motor.
 20. The aircraft of claim 11, furthercomprising: one or more fixed pitch blades attached to each of the threeor more variable-speed motors; and. wherein: the one or more of the oneor more fixed pitch blades are a different size; a torque of each of thethree or more variable-speed motors and the respective fixed pitch bladeis based on a size, power and position of the variable-speed motor andthe respective fixed pitch blade; he three or more variable-speed motorsand the respective fixed pitch blades are individually ducted; or a ringor cowling surrounds one or more of the three or more variable-speedmotors and the respective fixed pitch blades.